Composition and method for phosphate coating of metal



oxidizing the Fe++ to Fe+++.

United States H COATING F JMETAL Max Kronstein, New York, N. Y., assignor to Oakite Products, Inc., a corporation of New York N0 Drawing. Application 0ctober 4, 1957 15Serial-N0..688,125

Claims. 1(Cl. 148-.6.15)

. ettectivenessiof phosphate coating compositions and processes.

The chemical industry recognizes the needJof accelerators in the formation of phosphate coatings on metals and has utilized a number of approaches'to this goal. 'The usual methods rely on'inorganic oxidation accelerators,-such. as nitrates, forinstance, sodium nitrate. These are supposed'to form nitrites at the bathtemperature, and then to decompose in the presence of iron," thereby Soluble nitrites have also been used instead and 'chlorates have "beenimentioned. 7

Another approach .in, accelerating the';'metal.r' phosphatizing compounds has been 1the addition -of-salts-of .metals which are lower in .the-electromotive:series than the metals to be coated. Such salts were. those of copper,

.silver, molybdenum or. lead.

A thirdjapproach has-been the use of 'so-called -reduction accelerators, such 'as sodium bisulfite, or hydrosulfuric acid (H s- 0 or its salts.

,'Certain organic;additives also have been-used,- such as additives:containing nitrogen (aniline; to1uidine, =-pyri- 'dine) oramin-salts, or organic-compoundshaving a constitution similar tofalizarine -'or oxychlnoline.

, Others have added organic. derivatives of selenium,

such, as its saccharates,,glyconates, or glycerates. Also .certain otherorganic compounds have;been used,'such"as sugar, starch, or other"OH-containi.ng compounds.

Tannins. such.as quebracho .extract, which'hasj;been

The use of the most-efiiective,of these bark extracts is limited in the amount *of' possible concentration in the al phosphatizin'gisolution,vbecause of :the -fact,;that {the extra'c-tsszare: soluble in water: or insodium phosphate-molations only to a smallzextent.

tfAll fithese additives 1have "beenintended to 1 incorporates some specific 'squality:;-intof the .-metal fphosphatizing 'rcompounds. .1- In many cases very small 'amounts ,oftthe additives were applied.

T?The.;presnt*lHVCIl'ElOIinlS ;aimed at incorporating; into thetreating -solutionswcompounds having-=a -generally .Zhlgh6fil6V6130f chemical -reactivity, such components:be,ing

added in such an amount :as -to. form anqessential part of the total solids in the treating material.

I have discovered 'that'fthe addition of unsaturated -alcohols containingatdeast one triple bond,:and.,at least '.-one-..I- Ij-.'group,:or, preferably, unsaturated, polyhydro ry ealcoholsucontaining at least. one triple bond, under-such conditions astotbesoluble, to the extent of. at least about one part in three parts of water, improves 'the'efiective- Sept- 30,

'ness of phosphate coating solutions. If such alcohols are ICOMBOSITION AND 'METHOD FORIHOSBHATE able. The naturally solubleor solubillzed alcohols then form an accelerator which aids in'the formation of a more satisfactory phosphate coating on" metals such as iron and steel.

1 Some of: the accelerating compounds a are known Y in the art as tertiary acetylenic alcohols, such as CHa 1 C 8 ...CHs----.. ECT t-. H|

Dimethyl-hetynediol CH3 CH3 'CHfiCHz-7-CEC- 'CHr-CH;

. Dimethyl-oetynediol The 0H- groups -may-form:,part-.,of alstraightchain LCHE . none; onmoreshydroxyl- .=groups; can bemused.

As a suitable amount of.,these-.materials, their content in the complete coating solution should amount to at anleast onezpercent of the total' solidscontent-of; the complete phosphatizing compound.

I Where the alcohols are not su'fliciently soluble, 1 they mmay be solubilized by the addition of other-:alcohols of .athetsame type, of formamide,-or--of:-alkyl substituted formamides asuch as methyl formamide.

uWhen tformamideis used, it may-also: be desirable'to -za'dd zcertainacids or their anhydridesonsalts, particu- :-..larly. molybdic, tungstic andvanadic acids, which, as is .:;described in my application'entitled' Increasing the Solubility :of Metal Accelerators in Phosphatizingissolutions,

tracts first in. a. Water solubleorganic, amide, such .as fformam1de,,and by. then diluting thissolutionwith Water arid. rnal ging it partof the phosphatizinglsoll tion.

; The ,following :examples represent the formation, of

..- aqueous .solutions of. the: alcohols for use in, making ,up

phosphate; coating 5 solutions.

;Exa1mple -I In cases where the triple-bond alcohol is water soluble, a 1:1 solution in water-ismade and this solution is added 10.1116 Omp ncnts. of t e p o p ati n solutio This Lean ,bel onew h t the pp on f. j tf r s nc in the case of the propargyl' alcohol (HCzc- CH OH) Example II Where the solubility is of a lesser order, as in the case of dimethyl-hexynediol, a solution may be made contsasmng 1 gram of thealcohol in 3 grams of water at V i Example III Where the water solubilityis of'a still lower order,

clear solutions can be obtained by the use of additives.-

for instance, dimethyl-octynedi-ol is dissolved in 1:1 ratio in propargyl alcohol at around 45 C. This solution is diluted 1:1 with water, and aclear solution is obtained.

Example IV One gram of dimethyl-octynediol is dissolved in 2 grams of water at 55 C. and no clear solution was obtained. 0.5 gram formamide are added. Upon mixing, the solution becomes clear. When diluted with 20 tional water, the solution remains clear.

Example V Two components of different solubility are used as follows: 1 gram of 2 butyne-1.4 diol is dissolved in 2 grams of water at 45 C. To this solution 2 grams of dirnethyl-octynediol are added. No clear solution is obtained. Upon adding 0.4 gram of formamide, the solution becomes clear and, when diluted with 25 grams of water, it remains clear.

Example VI culated in a spray application tank and used as a spray solution in a phosphatizing process.

Example VII The procedure is as in Example VI, except that instead of 6.8 grams of hexyndiol, a mixed solution is used containing 3.4 grams of hexyndiol and 3.4 grams corn sugar.

Example VIII One gram of hexyndiol is dissolved in 2 grams formamide at 55 C.

0.2 gram of vanadium pentoxide are dispersed in this solution at 60 C. A mixture is obtained of dissolved and not-fully-dissolved metal oxide, which is added to 25 grams of water. This water solution is light yellow and a slight sedimentation, yellowish in color, appears. Upon addition of 5 grams of monosodium phosphate and 25 grams of water at approximately 95 C., the solution becomes colorless with a fine cloudy appearance. The fine sludge also is colorless. Upon addition of a few drops of 85% phosphoric acid the solution clears to a cloudless state.

Example IX Example X The procedure was as in Example IX, except that 14 i grams of dirnethyl octynediol was used instead of hexyngrams addi- 4 diol. The resulting pH of the solution was between 3.5

and 4.0. It was adjusted before application to a pH of 4.4, using a NaOH solution for the adjustment.

Example X I vanadic pentoxide.

The following examples show how formamide may be used for increasing the solubility of difiicultly soluble tannins.

Example XII 7 ing qualities of the resulting phosphate coating on steel as a base for an 'OD enamel paint film of approximately 1 mil thickness under salttog exposure were considerably increased by the entering into solution of such soluble organic matter from thequebracho extract, as had been capable of entering the solution in view of its very limited solubility. I

According to the invention, the concentration of soluble organic active matter is increased by first dissolving the 9.3 grams of quebracho extract in 13 grams of form amide. A solution is obtained which shows very little or no sedimentation and which can be diluted with water without precipitation of the organic material.

The quebracho-formamide solution, or its water diluted .form, is made a part of a metal phosphatizing compound,

such as 230 grams of monosodium phosphate, 6 grams of a wetting agent (Triton X45) and 4 grams of phosphoric acid, which is diluted before or after the addition of the quebracho solution to a desired treating concentration, for instance, to 4 gallons, and which is applied to steel surfaces in the usualtechnical manner.

This increase in concentration of the active organic 1 matter increases the paint bonding qualities of the coating.

In comparing the paint bonding life of these surfaces with those produced with a low-concentration quebracho-containing phosphatizing compound (without the use of this invention), the effect of the invention is clearly evident.

Example XIII 6.5 grams of sumac tannin were boiled in 60 grams of water. Most of the material remained undissolved and the filtrate was only slightly colored.

6.5 grams of sumac tannin were heated with 20 grams of dimethyl formamide and 8 grams of formamide. Nearly all the tannin was dissolved. A dark brown filtrate was obtained.

One-half of this filtered solution was diluted 1 to 4 with water. The other half was further diluted 2 to 1 withformamide, and this solution diluted with water. Clear solutions were obtained.

Example XV A number of types of triple-bond alcohols have been described above, such as the tertiary acetylenic alcohols with more than one OH group of a type which can be described as a form of acetylenic glycols, or straight chain "alcohols with one OH group, or alcohols with one or more OH groups where theqOH group was located indifferent position.

v The present example uses .a hexyndiol where the two methyl. groups of the dimethylhexyndiol (Example VI.) were replaced by two. phenyl groupsfithat is, the diphenyl' hexyndiol' was used; It was used in the. following formulation: 14 grams. of diphenyl, hexyndiol, were dissolved in .100 milliliters of water. 230' grams. of monosodium phosphate anhydrous and"9 grams of wetting agent '(Tween 20) were added" together with. an increase of the water to '1000 milliliters. At first a solid. crust was formed, which was dispersed inthe'coatingmaterial, then 2:5 grams ofmo'lybdic anhydride were. added with further stirring; and the resulting. product, further diluted'to 4' gallons, .was sprayed on 1010 steel in. a pressurespray. laboratory: unit, followed by the. usual chromic oxide rinse. Asatisfactory coatingonsteelwas obtained;

Six panels were. coated, and-then the; coating. was strippedoff again-by immersion in. a. solution of 600 milliliters ofr'hydroc hloric. acid (37.21%) and 300 milliliters of formaldehyde. The. weight, lossv of the. panels was determined. to. give the. amount. of coating which had been formed on these. panels.- By dividing the re sulting weight difference, in; milligrams, by the. square footarea. on which. this. coatinghad been formed, it was found that the. panels. had a coating, weight of 103.4 milligrams .per square foot, which is. considerably higher than coating weights. generally produced without triplebond. alcohols.

'The current tentative. and proposed Government specifications, such as. the. proposed Military Specification of the. AnnylOrdnance. Department for the; Treatment of Metal. Surfaces. with Iron Phosphates. prior Painting, and the 'Tentative Frankford Arsenal Purchase Description for the Cleaning, Preparation and varnishing of Steel Cartridge Cases (January 28, 1953), do not expect higher coatingv weights for such phosphate coatings than hetweerr 4.0. and 80 milligramsper square foot. The results-of. the example surpassathesecurrent expectations.

- Example- X W To facilitate the dispersion of the unsaturated alcohol, 14 parts diphenyl hexyndiol are dissolved in 60 parts of dimethyl formamide and 2.5 grams of molybdic anhydride are dispersed in 40 grams of dimethyl formamide. These dispersions are added to a heated solution of 230 grams of monosodium phosphate anhydrous and 9 grams of wetting agent in 1000 milliliters of water at about 80 C. with a strong agitation. This solution is further diluted with warm Water at around 80 C. to 4 gallons and applied in the spray chamber as in Example XV.

Again a satisfactory phosphate coating was obtained. Again six panels were weighed, their coating was removed and the weight difference determined in milligrams and this weight of the dissolved coating was divided by the square foot area of coated surface. The determined coating weight was 96.3 milligrams per square foot, that is again considerably above the expected coating weight for similar specification phosphate coatings without triple-bond alcohols.

Example XVII As an example for a single OH group triple-bond alcohol containing an aromatic group the phenyl butynol was used, whose formula can be described as CaHs euro-c5011 14 grams of phenyl butynol was dissolved in 100 milliliters of water. 230 milliliters of monosodium phosphate anhydrous and 9 grams of wetting agent (Tween 20) were added together with an increase of the water to milliliters. After fthedispersion had been ob,- tained, 2.5 grams of molybdic, anhydride were added with stirring and theresultin'g product was further vdiluted to 4 gallons and'was.spraye'd on 1010' steel" panels, followed by the usual chromic acid rinse.

Again 'asatisfactory coating was obtained and the coatingweight. was determined" as described in Example XV. The obtained coating weight was in this case 9,1.5 millijgrams per squarefoot.

Exam le XVIII The same phenyl butynol was used in accordance. with the method shown ini Example XVI, and again a; satisfactory coating -was, obtained. The stripped; coating weight was, in this case 97. .1 milligrams per square. footi Having shown in theseexamples how the-invention is applied in typical cases, the effect of the invention can further be presented. But diiferent forms of: the applicationior compositions can be-used besides those shown in. the; examples.

With the new invention using. active organicamaterials which are water solublev or which have been brought into, a water soluble combination, or using reactive 'organic materials of limited; solubility i'n'water, but' in-. creasing their concentration. in water solutions. by the application of formamide and its derivatives, more effectivephosphatizing. compounds can be produced. More uniform. coatings are obtained, and, where desirable, higher coating; weights can. be achieved than were ob tained from. identical solutions. having a lower con'ce'n tration of reactive organics or having no organics at all;

In applying a gilsonite asphalt-linseed oil test lacquer as testfilm over suchcoatings, the film adhesion was superior under saltfog exposure to'comparative phosphate coatings .produced without' the'use of this invention.

. The increased? coating: weights: of these materials have a better impact resistance than commercial zinc-phosphate coatings of'similar coating weights. 7

When. phosphatized: metal surfaces have been exposed for two or more days before p'aint application, they show generally a decrease in paint adhesion when tested with such. thinv films' as the-'gilso'nite asphalt film. The invention provides for phosphate coatings which are less sensitive in this respect and so allow a wider time-interval between phosphatizing and paint application.

In measuring the profiles produced by commercial phosphate coatings and those based on the invention, the new surface profiles, as measured with such instruments as the brush surface analyzer, show a uniform development on various areas of the panels on the surface coated with new compounds, which are more uniformly developed than on other materials tested. I

Measurement of the degree of insolubilization which occurs in the application of the water-spray solution on the metal surface which has been sprayed, shows that the new active groups produce a considerable degree of insolubilization when measured by conductivity measurements. These are performed by immersing the panels in water of known electrical resistance and measuring in short time intervals the decrease in resistance by the dissolving of the unconverted materials. Compared with comparative treatments without the new components or without the increased content in reactive limited-soluble organic components, the new surfaces show a considerably slower drop in electrical resistance during the usual test period of 3 minutes.

While in the examples formamide has been mentioned as a solubilizing agent, derivatives of formamide in which one or both of the hydrogens in the NH group have been replaced by other radicals, and especially the alkylsubstituted formamides such as methyl formamide may be used in substantially the same proportions. Those compounds are preferred which are liquid below 100 C., and which leave behind no harmful residues when the coating is rinsed in the conventional manner and then 7 heated to dryness. Formamide is especially useful in this respect since all its elements are volatile and are driven ofi when the coating is heated.

While quebracho and sumac extracts are given by way of example above, other tannins are also effective in improving the application of phosphate coatings, especially other plant bark extracts which are of limited solubility in phosphatizing baths containing non-ionic wetting agents. In general, these appear to be tannins having catechol residues, such as chestnut and catechu extracts.

This application is a continuation in part of my application Serial No. 499,749, filed April 6, 1955, now abandoned.

While I have described herein some embodiments of my invention, I wish it to be understood that I do not intend to limit myself thereby except within the scope of the claims hereto or hereinafter appended.

I claim:

1. A phosphate coating composition consisting principally of water and at least one phosphate coating agent selected from the group consisting of phosphoric acid and salts thereof, said composition containing at least about one percent of an accelerator consisting essentially of an unsaturated alcohol containing at least one triple bond, said accelerator being soluble to the extent of at least one part in three parts of water.

2. A phosphate coating composition consisting principally of water and at least one phosphate coating agent selected'from the group consisting of phosphoric acid and salts thereof, said composition containing at least about one percent of an accelerator consisting essentially of an unsaturated alcohol containing at least one triple bond, said alcohol being less soluble in water than one part in three parts of water, said accelerator including at least one substance selected from the group consisting of formamide and alkyl-substituted formamides in an amount sutficient to render the alcohol soluble to the extent of at least one part in three parts of water.

3. A composition as claimed in claim 2 further containing at least one compound selected from the group consisting of molybdic, tungstic and vanadic acids and the anhydrides thereof.

4. An aqueous solution containing an unsaturated alcohol containing atleast one triple bond in an amount substantially, greater than the amount which is soluble in water alone and at least one compound selected from the group consisting of molybdic, tungstic and vanadic acids and the anhydrides thereof in an amount greater than is soluble in water alone, and at least one substance selected from the group consisting of formamide and alkyl-substituted formarnides in an amount sutficient to render such alcohol soluble in water.

5. A solution as claimed in claim 1 further containing at least one compound selected from the group consisting of molybdic, tungstic and vanadic acids and the anhydrides thereof.

6. Acoating solution as claimed in claim 5 further containinga wetting agent.

7. A method of phosphate coating metal surfaces which comprises bringing into contact with such surfaces 3 phosphate coating composition as claimed in claim 1.

8. A method of phosphate coating metal surfaces which comprises bringing into contact with such surfaces a phosphate coating composition as claimed in claim 2.

9. A method asclaimcd in claim 8 in which said solution further contains at least one compound selected from the group consisting of molybdic, tungstic and vanadic acids and theanhydrides thereof.

10. A method of increasing the solubility in water of an unsaturated alcohol containing at least one triple bond and of at least one compound selected from the group consisting of molybdic, tungstic and vanadic acids and the anhydrides and salts thereof, which comprises dissolving the alcohol and the compound in at least one substance selected from the group consisting of formamide and alkyl-substituted formamides and adding the resulting solution to water, the compound being present in an amount greater than is soluble in water alone.

References Cited in the file of this patent UNITED STATES PATENTS Dodd et al. Apr. 4, 1950 

1. A PHOSPHATE COATING COMPOSITION CONSISTING PRINCIPALLY OF WATER AND AT LEAST ONE PHOSPHATE COATING AGENT SELECTED FROM THE GROUP CONSISTING OF PHOSPHORIC ACID AND SALTS THEREOF, SAID COMPOSITION CONTAINING AT LEAST ABOUT ONE PERCENT OF AN ACCELERATOR CONSISTING ESSENTIALLY OF AN UNSATURATED ALCOHOL CONTAINING AT LEAST ONE TRIPLE BOND, SAID ACCELERATOR BEING SOLUBLE TO THE EXTENT OF AT LEAST ONE PART IN THREE PARTS OF WATER. 